72 
MR. T. E. STANTON ON THE PASSAGE OF HEAT BETWEEN 
Tills result agrees remarkably with the results of Professor PtEAPsroLDs’ experiments 
on the change of the law of resistance in pipes, in which he found a range of unsteadi¬ 
ness in the preamre lying between 
and 1 ‘3 V^.. 
Description of the Apparatus. 
For the purpose of the experiments, three drawn copper tubes were obtained, the 
thickness of the metal lieing '08 centini., the length 48 centims., and the internal 
diameters lining 1'39, 1-07, and '736 centims. respectively. 
As it was necessary that the velocity of the jacket water should be as high as 
possible, in order that the motion in the jacket might be “eddying” (the critical 
velocity for such a case not having been yet determined), the distances between the 
outer surfaces of the pipe and the inner surface of the jacket was made as small as 
possible, consistent with the possibility of getting the required amount of ivater to 
flow through under the available pressure. 
The jacket pipes were of brass, the width of the jacket space being 
‘165, ’065, '16 centini. 
for the three cases. 
'fo insine a uniform density of the water at any cross section, it was necessary to 
place the pipes in a vertical position, and, to make the motion of the water as unstable 
as possible, the water flowed downwards in each case. 
The water used was obtained from a large tank in the tower of the College 
buildings, the head available being about 100 feet, which remained practically constant 
throughout the experiments. It was found that the supply from the Town’s main 
was useless, owing to the varying pressure in the mains causing the flow to be 
unsteady. 
Measurement of the Water. 
To estimate the Cj[uantities of water passing through the pipe and jacket, two 
meters were required which would give correct values of the amount of water passing 
through them at aii}^ instant, and which should be sensitive, i.e., would indicate at once, 
the change in the flow due to an adjustment of the water valves. 
In the early experiments, the water ran into cylindrical vessels with open tops, and 
tliin lipped orifices, through which the water was discharged ; the discharge being 
estimated from the head of water in the vessel. 
The objection to this form of meter is that the change in the “ head,” due to an 
alteration of the valve, takes place slowly, in some cases nearly a minute elapsing 
before the head of water in the vessel attains its new position. Consequently the 
